This invention relates to railroad undertrack maintenance equipment, and, more particularly, to apparatus for laying fabric under raised portions of track.
Railroad track beds must be carefully prepared before rails and ties are positioned, so as to obtain the firmest possible foundation for the track. Ballast consisting of crushed or coarse rock is applied on top of subgrade materials, the ballast serving as the bed on which the track is placed. It has been the practice to treat the ballast with lime or other chemicals to achieve cohesiveness, so as to prevent the ballast from sinking into the subgrade. More recently, a continuous layer of fabric has been applied over the subgrade before the ballast is layed, the fabric serving as a barrier between the ballast and subgrade. The use of protective fabric in such manner has greatly improved the durability of track beds, and has significantly lowered the cost of bed preparation, compared to lime and similar treatments.
The laying of fabric under existing tracks presents obvious difficulties. At present one practice is to lift a section of track and move it to one side. Workmen then place a roll of fabric on the exposed bed, after ballast has been removed, and unroll the fabric. After clean ballast is applied, the raised track is then moved back over the bed and set on top of ballast covering the fabric. This process is repeated over and over again until the entire rail section has been covered. In another method, ballast is removed beneath track and a device is inserted to raise the track approximately 15 to 20 inches, which allows insertion of a small roll of fabric. As the device is moved forward, fabric is unrolled onto the cleared track bed. Such techniques require considerable manpower, leading to high application costs.
Presently available maintenance equipment consists of machines having boxlike frames and being capable of riding along the track while performing a variety of maintenance operations, including the plowing out of crib material, the removal of reject ties, the realigning of track, and the smoothing of the track bed. Such machines are also used to raise the track above the ground to allow workmen to apply fabric, as noted, but they have not been adaptable for laying the fabric continuously as the equipment moves down track. That is, none of the presently available undertrack maintenance machines can be used to continuously unroll and apply fabric under existing track without the use of workmen to manually position the fabric roll under the track structure. Also, the fabric roll used conventionally must be of a small diameter, usually no more than about 20 inches, such that it can fit within the limited space between the raised track and the track bed.
Conventional apparatus for applying fabric under raised track is disclosed in Scheuchzer, U.S. Pat. No. 4,004,524. A small roll of fabric is disposed under the raised track and unrolled onto the prepared track bed as the undertrack maintenance machine progresses. Such apparatus cannot use large diameter fabric rolls, which means that workmen are required for frequent replacement of fabric rolls.